Reader: compare button next to Aa

A button beside Aa in the reader's top bar opens a Compare translations
sheet (pick the Bible to compare with, show/hide the differing-word
highlights). It shows as active while a comparison is on. The controls
moved out of the Aa sheet; "C" opens it from the keyboard.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/pages/ReaderPage.test.jsx

@@ -47,6 +47,17 @@ test('renders the chapter, chrome and opens the tool sheets', () => {
   expect(screen.getByPlaceholderText(/Search John 3/)).toBeTruthy();
 });
 
+test('the compare button next to Aa opens the comparison sheet, and choosing a Bible turns it on', () => {
+  ctx.setReaderParallel = vi.fn();
+  render(<ReaderPage />);
+  const compare = screen.getByLabelText('Compare translations');
+  expect(compare.nextElementSibling).toBe(screen.getByLabelText('Reading settings')); // sits right beside Aa
+  fireEvent.click(compare);
+  expect(screen.getByText(/how different its wording is/)).toBeTruthy();
+  fireEvent.click(screen.getByRole('button', { name: 'NET' }));
+  expect(ctx.setReaderParallel).toHaveBeenCalledWith('NET');
+});
+
 test('tapping a verse selects it', () => {
   render(<ReaderPage />);
   fireEvent.click(screen.getByText(/This man came to Jesus/));